Internal combustion engines utilize valve lifters that operate in conjunction with cams of a camshaft to reciprocate valve lifters. Typically, as the camshaft rotates, the cams of the camshaft operatively engage an end of the valve lifter to reciprocate the valve lifters in an internal combustion engine. The valve lifters are located within cylindrical bores in an engine block. The engine block provides a travel passageway for each valve lifter and allows oil to lubricate each lifter assembly. Oil is directed to injection ports by a straight and common transverse oil passageway that intersects the injection ports.
Various valve lifter designs have been developed for specific engine environments. Hydraulic valve lifter assemblies and solid lifters are typically used for engines having relatively low revolutions per minute. Roller valve lifters (or roller lifters) utilize a roller to contact the cams of a camshaft and are typically used in engines having relatively high revolutions per minute. The use of a roller to contact the cams reduces wear and extends the useful life of both the valve lifter and the cams of the camshaft.
However, a problem commonly associated with valve lifters is the need to provide oil to the lifters as they reciprocate within the valve bores and to the valve lifter rollers and cams of the camshaft as the lifters ride on the cams. When using roller lifters, it is important to provide a sufficient supply of oil to the rollers and cams particularly at the point of contact. A known approach to increase the oiling of these areas is to provide an oil pressure feed groove or supply area on the surface of the roller lifter. This oil pressure feed groove is typically an annular groove or indented band on the circumference of the tappet body of the valve lifter. Oil enters the oil pressure feed groove from the common transverse oil passageway in the engine block that intersects the valve bores. As the roller lifter reciprocates within the engine, the oil pressure feed groove carries oil up and down the roller lifter bore and also directs oil towards the roller of the roller lifter that engages the cam. Although this method serves to provide some quantity of oil to the rollers and cams, in an engine having high revolutions per minute, there is a need to maximize the quantity of oil flowing to the rollers and cams to decrease roller and cam wear.
Another problem associated with engines having high revolutions per minute and using roller lifters is the need to supply adequate oil to the roller bearings of the roller lifter. Inadequate oiling of the roller bearing results in excessive wear and may lead to catastrophic failure of the bearing, and consequently failure of the entire engine. A known approach to oiling the roller bearings is to provide an oil supply port on or in an oil supply band area that receives oil directly from an engine oil supply gallery. Both of these areas are exposed to debris which is commonly found in the oil system. This debris can easily clog the oil supply port, thereby causing damage to the roller lifter and the engine.
Therefore, a need exists for a roller lifter having an improved oil injection port and supply groove that is located away from the oil supply band area and the engine oil supply gallery where debris commonly travels, thereby preventing the introduction of debris into the oil injection port and possible clogging of the oil injection port.